The present invention relates generally to a valved combustor or combustion wave rotor, and in particular to a valved combustor or combustion wave rotor having partitions at the inlet thereto.
Combustion engines offering superior performance are highly desirable for use in power generation, ground transportation, and air vehicle propulsion. It is desirable to simultaneously improve engine efficiency and reduce harmful emissions of nitrogen oxides (NOx), other pollutants, and greenhouse gases. Conventional gas turbines based on steady-flow turbomachine components, and conventional internal-combustion engines based on semi-static mechanical compression and expansion, have fundamental thermodynamic or throughput limitations on performance. It is particularly desirable to provide gas turbine engines and jet engines with a combustion device that produces a gain in pressure during combustion, while retaining high throughput, in order to maximize power output and efficiency. It is also desirable to provide engines which are environmentally acceptable and minimize pollutants such as NOx emissions.
A quantum increase in engine performance is possible by developing dynamically non-steady processes and devices that exploit wave phenomena and intermittent pressure-gain combustion for novel engines. By understanding and exploiting complex non-steady flow it is possible to simplify the hardware of the engine, making it less costly and more durable. Such flow and combustion processes can be realized in either a combustion wave rotor or in a valved combustor.
Combustion processes that improve engine efficiency can benefit from high pressure and temperature, which in turn, however, create heat management problems and pollutant emissions in the combustion device. Thus, it is desirable to provide a combustion device which is capable of operating at elevated temperatures with short residence times to reduce pollution emissions and which also provides proper heat management.
The present invention overcomes the existing problems by providing an internal combustion device, such as wave rotor or rotary-valved combustor, having reduced pollution emissions and using circumferential partitioning to effect heat management. In particular, the circumferential partitioning permits a non-combustible gas to be placed adjacent to the hub and shroud to reduce the leakage of hot gas from the inlet side of the combustion chambers and to also help cool the combustion device. The present invention also improves combustion wave rotors and valved combustors by providing a partitioned multi-channel combustor that minimizes NOx pollution through a method of pilot ignition. The present invention provides a promising means of pressure-gain combustion, which approaches the thermodynamic ideal of constant-volume combustion, providing significant enhancement of gas turbine and jet engine performance.
A multi-channel combustor is provided to create pressurized hot gas by detonative or deflagrative combustion for turbine rotation or jet propulsion. In general, a combustion device of the present invention includes a housing having at least one inlet port. A plurality of combustion chambers are mounted within the housing. The chambers each have an inlet end for gaseous communication with the inlet port. The inlet end of a chamber has a fuel partition injection region. At least one inlet zone is disposed within the inlet port. The inlet zone may optionally be sized to communicate substantially with only the fuel partition injection region at the inlet end of the chamber. The inlet zone includes partitions to partition the inlet zone into separate channels, for example, in the radial direction relative to a longitudinal axis of the combustion chambers. At least one channel is adapted to register with the fuel partition injection region of the combustion chamber. A first specific configuration of the combustion device provides a combustion wave rotor, and a second configuration provides a valved combustor.
The combustion wave rotor is an on-rotor combustion device where the combustion process occurs within the combustion chambers of the rotor, creating detonative or deflagrative combustion within the rotor. The combustion wave rotor includes a housing, one or more inlet ports in the housing, one or more exhaust ports in the housing, a rotor mounted within the housing, one or more igniters, and, optionally, a motor for rotating the rotor. The rotor includes a plurality of combustion chambers in which combustion occurs. Each combustion chamber has an inlet end for communication with the inlet port and has an outlet end for communication with the exhaust port.
To promote the creation of detonative or deflagrative combustion, a plurality of separate inlet zones may be provided in the inlet port for supplying fuel and air mixtures to the inlet end of the combustion chambers. The inlet zones are circumferentially spaced about the perimeter of the combustion chambers so that the combustion chambers interact with these inlet zones sequentially as the combustion chambers or inlet zones rotate past one another. At least one of the inlet zones has circumferential partitions to segment the inlet zones in the radial direction. A fuel injector is provided in selected inlet zones for injecting fuel into each respective zone. Each inlet zone is capable of introducing a different combustible mixture sequentially into a given combustion chamber as the chamber comes into communication with a respective inlet zone. For example, a first inlet zone may be provided to introduce air, without fuel, into the chamber. As the combustion chamber is brought into registry with a second inlet zone, a fuel or fuel mixture may be introduced into the chamber. Additional inlet zones may be provided for successively introducing additional fuel or fuel mixtures, which may be different from other fuels or fuel concentrations, into the chamber. Another inlet zone, such as the last inlet zone, may introduce a combustion enhancer or a mixture of fuel and the combustion enhancer into the combustion chamber proximal to the source of ignition, to enhance detonative combustion. Using successive inlet zones results in the stratification of differing concentrations of combustible material within the combustion chambers.
The combustion chambers optionally include circumferential partitions that may closely align with the circumferential partitions in the inlet zone, and may extend from the plane of the inlet end into the chamber approximately one-twentienth to one-fifth of the length of the chamber in the longitudinal direction. These partitions create a small pilot-ignition volume within the combustion chamber that momentarily contains a mixture that is particularly well suited for ignition and allows the combustion of a fuel-lean mixture in the remainder of the combustion chamber, resulting in lower NOx emissions.
These partitions also allow a non-combustible gas such as air to be introduced in the region of the combustion chamber near the inlet from which leakage may occur during combustion and pressurization in the chamber. The placement of a non-combustible gas adjacent the hub and shroud can substantially eliminate the leakage of hot gas from the inlet side of the rotor and also help to cool the rotor. This can minimize thermal damage of the bearings and other components of the wave rotor, as well as provide a further level of control of the rotor temperature and its gradient. In addition, the most readily ignited mixture may be supplied only to the central section to avoid preignition by hot gas leaking into the low-pressure inflowing gas.
The initiation of detonation is improved by providing a more confined location for containing a detonation susceptible gas mixture which permits less ignition energy to initiate detonation. Detonation initiation and propagation processes have channel size requirements that may be smaller than the height of the main combustion chamber. Also, initiation of detonation can be aided by additional turbulence generated by geometric irregularities in the partitions. The use of circumferential partitions in the combustion chamber permits control of this dimension in the initiation phase.
The present invention is particularly well-suited to a combustion wave rotor. The inlet and exhaust aerodynamics of a wave rotor are superior to those of a valved combustor. However, a valved combustor, having a non-rotating part that is xe2x80x9cloadedxe2x80x9d with pressure and heat, has mechanical and thermal advantages over the wave rotor. The stationary combustion chambers of the valved combustor can have more robust construction and cooling methods than the rotating combustion chambers of the combustion wave rotor. The preferred choice will depend on the application and economic factors.
Consequently, the present invention also provides a valved combustor where the combustion process occurs within stationary combustion chambers. The valved combustor includes a housing, a plurality of combustion chambers mounted within the housing, a rotor mounted within the housing, one or more inlet ports mounted on the rotor, one or more exhaust ports mounted on the rotor, and one or more igniters mounted at the housing to communicate with the combustion chambers. The combustion chambers extend longitudinally relative to the rotational axis of the rotor. Each combustion chamber has an inlet end for communication with the inlet port of the rotor positioned at one end of the combustion chambers and an outlet end for communication with the exhaust port of the rotor positioned at the other end of the combustion chambers.
To promote the creation of detonative or deflagrative combustion, a plurality of separate inlet zones may be provided in the inlet port of the rotor for supplying fuel and air mixtures to the inlet end of the combustion chambers. The inlet zones are circumferentially spaced about the perimeter of the combustion chambers so that the combustion chambers interact with these inlet zones sequentially. The inlet zones have circumferential partitions to segment the inlet zones in the radial direction. A fuel injector is provided in selected inlet zones for injecting fuel into such respective zones. Each inlet zone is capable of introducing a different combustible mixture sequentially into a given combustion chamber as the inlet zone rotates past the combustion chambers. For example, a first inlet zone may be provided for providing an introduction of air, without fuel, into the chamber. A second inlet zone is subsequently brought into registration with the combustion chamber by rotation of the rotor. The second inlet zone may introduce a fuel or fuel mixture into the chamber. Additional inlet zones may be provided for successively introducing additional air or fuel mixtures, which may be different from other air or fuel concentrations, into the chamber. Another inlet zone, such as the last inlet zone, may introduce a combustion enhancer or a mixture of fuel and combustion enhancer into the combustion chamber proximal to the source of ignition to enhance combustion. Using successive inlet zones results in the stratification of differing concentrations of combustible material within the combustion chambers.
The combustion chambers optionally include circumferential partitions that may closely align with the circumferential partitions in the inlet zone, and may extend from the plane of the inlet end into the chamber approximately one-twentienth to one-fifth of the length of the chamber in the longitudinal direction. These partitions create a small pilot-ignition volume within the combustion chamber that momentarily contains a mixture that is particularly well suited for ignition and allows the combustion of a fuel-lean mixture in the remainder of the combustion chamber, resulting in lower NOx emissions. These partitions also allow a non-combustible gas such as air to be introduced in the region of the combustion chamber near the inlet end from which leakage may occur during combustion and pressurization in the chamber. This allows leakage of low-temperature air and prevents leakage of hot gas.
The rotor is provided with appropriate rotary seals or other means that allow the passage of fuel and combustion enhancer into passages in the rotor, as required for the supply and injection of fuel and combustion enhancer to inlet zones located in inlet ports mounted on the rotor.
For both the wave rotor combustion engine and the rotary-valved combustor, the length of the combustion chambers, the circumferential width of the inlet and exhaust ports, the placement of the exhaust port(s) relative to the input port(s), and the rotational speed of the rotor are designed to control the cyclic flow processes, wave processes, and combustion processes to support combustion within the combustor. A CPU or electronic control system is optionally provided to control the rates of the rotor rotation, fuel injection, and ignition.